1. Field Of The Invention
This invention relates to an electromagnetic relay used for working a movable contact and for opening and closing an electric circuit by exciting a coil.
2. Description Of The Prior Art
Heretofore, there has been used an electro magnetic relay as shoen in FIG. 5, for example.
This conventional relay 100 shown in the figure is fixed with terminals 103 and 104 having fixed contacts 101 and 102 facing each other to a base 105 and is fixed to the base 105 with a frame 106 for forming a magnetic path. Said frame 106 is attached with a coil 107 for excitation.
A L-like shaped conductive plate 108 having stiffness is engaged to a projection 106a provided on the upper side of the frame 106 in FIG. 5 at one end thereof, and is attached to an armature 109 at another end thereof. The armature 109 is suspended in movable round the one end of the L-shaped plate 108 engaged to the projection 106a at the state in which the armature 109 is separated from an end 106b of the frame 106 by the plate 108.
A tension spring 110 is engaged between the upper end of the armature 109 and a hook 106c provided to the upper end of the frame 106 in the right side in FIG. 5, and said armature 109 is attached with a movable contact 112 through a movable contact plate 111. Said movable contact 112 is disposed so that an extension line A of the armature 109 in the directions of the terminals 103 and 104 may be parallel with extension lines B and B of the terminals 103 and 104 in the direction of the armature 109 approximately. And in this state, the movable contact 112 is so designed as to contact with or discontact from the fixed contacts 101 and 102 provided to the terminals 103 and 104 respectively.
And either end of a wound wire 107a of the coil 107 is connected respectively to terminals 113 and 114 fixed to the base 105, and one end of a lead wire 115 is connected to the movable contact plate 111 and another end of the lead wire 115 is connected to a terminal 116 fixed to the base 105.
In an unexcited state of the coil 107 as shown in the figure, the armature 109 is energized in the clockwise direction by elasticity of the tension spring 110 round the one end of the L-shaped plate 108 and the movable contact 112 is in contact with the fixed contact 101 in the left side in FIG. 5, so that the terminal 116 is connected electrically with the fixed contact 101 in the left side in FIG. 5.
In the state, supplying a prescribed electric current to the coil 107 through the terminals 113 and 114 by changing a switch (not shown), magnetic flux is generated by the excitation of the coil 107, so that the armature 109 is attracted rightward in FIG. 5. Thereby, the armature 109 moves rotatively in the anticlockwise direction against the elasticity of the tension spring 110, and the movable contact 112 attached to the armature 109 through the movable contact plate 111 separates from the fixed contact 101 on the left side in FIG. 5 and cones in contact with the fixed contact 102 on the right side in FIG. 5. Accordingly, the terminal 116 of the movable contact 112 is disconnected electrically from the fixed contact 101 on the left side in FIG. 5 and is connected electrically with the fixed contact 102 on the right side in FIG. 5.
And, in this state, intercepting the power supply through the terminal 113 and 114 for the coil 107 by changing the switch (not shown), the coil 107 becomes into unexcited state and discountinues to attract the armature 109. Therefore, the armature 109 moves rotatively in the clockwise direction by the elasticity of the tension spring 110, and so the movable contact 112 separates from the fixed contact 102 on the right side in FIG. 5 and comes in contact with the fixed contact 101 on the left side in FIG. 5. Thereby, said movable contact 112 returns to the state shown in FIG. 5.
Hereupon, said movable contact 112 moves along a line shown with arrow C in FIG. 5. Therefore, when the movable contact 112 comes in contact with the fixed contact 102 on the right side between the respective fixed contacts 101 and 102 shown in FIG. 5, said movable contact 112 comes in contact with said fixed contact 102 in sliding each other by downward displacement of the movable contact 112 together with the movable contact plate 111 because the armature 109 is attracted in the direction of the coil 107 against the elasticity of the tension spring 110 and moves rotatively round the one end of the L-shaped plate 108 in the anticlockwise direction. And, when the movable contact 112 returns to the fixed contact 101 on the left side between the respective fixed contacts 101 and 102 shown in FIG. 5, said movable contact 112 comes in contact with said fixed contact 101 in sliding each other by upward displacement of the movable contact 112 together with the movable contact plate 111 because the arm armature 109 returns in the opposite direction of the coil 107 by the elasticity of the tension spring 110 and moves rotatively round the one end of the L-shaped plate 108 in the clockwise direction. In this manner, said movable contact 112 is so structured as to contact with respective fixed contacts 101 and 102 in sliding each other in order to wipe dust or the like off the contacts and to reduce contact resistance between the contacts (the contact of this kind is called a sliding contact, a wiping contact or a self-cleaning contact).
However, in the above mentioned electromagnetic relay 100, because the armature 109 is designed so as to move rotatively in the clockwise or the anticlockwise direction round the one end of the L-shaped plate 108 by the elasticity of the tension spring 110 through said plate 108 in order to contact the movable contact 112 slidingly with the respective fixed contacts 101 and 102, the L-shaped plate 108 and the tension spring 110 are required for moving the armature 109 rotatively, therefore there is a problem since increase of the parts in number prevents to reduce the cost.
And, the armature 109 is desingned so as to move rotatively round the one end of the L-shaped plate 108 engaged to the projection 106a at the state in which the armature 109 is separated from the end 106b of the frame 106 by said L-shaped plate 108, therefore there is another problem in that attractive force of the coil 107 for the armature 109 is lost remarkably by the gap existing between the armature 109 and the frame 106.